As a compressor assembled in, for example, a refrigeration system of an air conditioning system for vehicles, a compressor incorporated with an oil separator, in which a centrifugal separation system oil separator is incorporated into a compressor, has been known (for example, Patent document 1). In a conventional compressor incorporated with an oil separator, for example, as is shown in FIG. 29 an example of a case of a scroll-type compressor which has a compression mechanism 103 comprising a fixed scroll 101 and a movable scroll 102, a centrifugal separation system oil separator 107 is incorporated into a rear casing 106 forming a discharge chamber 105 into which the gas (for example, refrigerant gas) compressed in compression mechanism 103 is introduced through a discharge hole 104. In such an oil separator 107, a structure is employed wherein a cylindrical cylinder (oil separation chamber 108) is provided in casing 106 as an oil separation section, on the axis thereof a separation pipe 109 is inserted or press fitted, and the upper end side thereof is fixed by or engaged with a snap ring 110. Because the oil separation section is provided only in casing 106 and the oil separation section is formed by machining, a seal bolt 111 is required in order to keep the inside pressure. Further, a discharge port 112 connected to outside of the compressor (external tube) is communicated with a space formed between the upper end of separation pipe 109 and the lower end of seal bolt 111.
The gas compressed in compression mechanism 103 is discharged into discharge chamber 105 through discharge hole 104 of the fixed scroll, and the oil-containing gas in discharge chamber 105 is introduced into oil separation chamber 108 through communication holes 113. The introduced gas rotates around separation pipe 109, and is separated into gas and oil utilizing centrifugal force. The separated gas passes through the inside of separation pipe 109 and is discharged from discharge port 112, and the oil separated by centrifugal force is stored in a lower oil-storing chamber 115 through a lower hole 114. The oil stored in oil-storing chamber 115 is returned to a suction chamber 117 through an orifice 116.
By the way, in the above-described oil separation structure, gas is likely to stay in a space above oil surface 118 of the oil stored in oil storing chamber 115, and there is a fear that the oil level is lowered and the amount of oil in oil storing chamber 115 decreases. In order to solve such a problem, it is necessary to discharge the gas in oil storing chamber 115 to outside. For example, in the compressor shown in FIG. 30 (Patent document 2), a structure is employed wherein gas release passageway 119 is provided between the side of a part 115a of the oil storing chamber, which is opened with lower hole 114, and the side of another part 115b of the oil storing chamber, which is not opened with lower hole 114, the gas stayed in the part 115a side of the oil storing chamber is introduced into the other part 115b side of the oil storing chamber, and introduced again into oil separation chamber 108 through lower hole 114, so that the gas can be discharged to outside from the inside of separation pipe 109.
In the compressor disclosed in Patent document 2, however, because the gas stayed in the part 115a side of the oil storing chamber is introduced into the other part 115b side of the oil storing chamber via gas release passageway 119 and further introduced into separation pipe 109, there is a fear that an efficient gas release from oil storing chamber 115 cannot be achieved sufficiently. Further, because it is necessary to form a groove with a complicated shape, etc. for forming the gas release passageway, the workability in production may be deteriorated.    Patent document 1: JP-A-11-93880    Patent document 2: Japanese Patent 3,847,321